The Parts of an Aircraft Electrical System

Many aircraft are equipped with either a 14- or 28-volt direct current electrical system. Some systems are more advanced than others, but the basic aircraft electrical system comprises the following components: alternator/generator, battery, master/battery switch, alternator/generator switch, bus bar, fuses, & circuit breakers, voltage regulator, ammeter/load meter, and the associated electrical wiring. In this blog, we will discuss the main parts of aircraft electrical systems.

Engine-driven alternators or generators supply electric current to the system and maintain a sufficient electrical charge in the battery. Electrical energy stored in the battery provides a source of electrical power for starting the engine as well as a limited supply of backup power in the event of an alternator or generator failure. At low RPM, most direct current (DC) generators do not provide enough electrical current to operate the entire electrical system. During operation at low RPM, the electrical power is drawn from the battery, which can be quickly depleted. Alternators offer many advantages over generators. For one, they produce enough current to operate the entire electrical system, even at low engine speeds. They do this by producing alternating current (AC) which is then converted to DC. The electrical output of an alternator is also more constant over a range of engine speeds.

Many aircraft have receptacles that connect to an external ground power unit (GPU) to provide electrical energy for starting. These are a significant help, particularly when starting during cold weather. When using a GPU, the manufacturer recommendations should be closely adhered to.

The electrical system is turned on and off by a master switch. When the master switch is turned on, electrical energy is provided to all electrical equipment circuits apart from the ignition system. Equipment controlled by the master switch typically includes the position, anti-collision, landing, taxi, interior cabin, and instrument lights, as well as the radio equipment, turn indicator, fuel gauges, electric fuel pump, stall warning system, pitot heat, and starting motor. With the switch in the off position, the entire electrical load is placed on the battery. All nonessential electrical equipment should be turned off to conserve battery power.

The bus bar is used as a terminal to connect the main electrical system to the equipment. It makes the wiring system more simple and provides a common point for voltage to be distributed throughout the entire system. Fuses and circuit breakers are used in the system to protect the circuits and equipment from electrical overload. The two devices have the same functions, but circuit breakers can be reset after an overload while fuses must be replaced.

Ammeters are used to monitor the performance of the electrical system. It displays if the alternator/generator is producing an adequate supply of electrical power, and indicates whether or not the battery is being charged. Ammeters are designed with a zero point in the center of the face and a negative or positive indication on either side. When the pointer of the ammeter is on the plus side, it shows the charging rate of the battery. When on the minus side, it means more current is being drawn from the battery than is being replaced. A full-scale deflection in either direction indicates a malfunction of the ammeter.

Another electrical monitoring indicator is the load meter. This type of gauge has a scale that begins at zero and displays the electrical load being placed on the alternator/generator. The load meter denotes the total percentage of the load placed on the generating capacity of the electrical system by the electrical accessories and battery. When all electrical components are turned off, it reflects only the amount of charging current demanded by the battery.

For all types of aircraft electrical system components and much more, look no further than Purchasing Management 360. Owned and operated by ASAP Semiconductor, we can help you find all types of parts for the aerospace, civil aviation, defense, electronics, industrial, and IT hardware markets. Our account managers are always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick & competitive quote, email us at or call us at 1-714-705-4780. Let us show you why we consider ourselves the future of purchasing.


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